Study Of Laser And Water-jet Combined Etching For Crystalline Silicon

The method of water-jet and laser composite etching method use the heat removal capacity of laser as main processing method, tuse of the cooling effect of the water jet to reduce the thermal stress gradient, reducing crack brittle material defects. At the same time the impact produced by low-pressure jet can remove the slag timely, than improve processing quality, and improve processing efficiency indirectly. However, the combined etching method involves too many parameters which has certain correlation between them. It still need a deeper study in order to play the superiority of this combine etching method better. In this paper, water jet assisted laser composite processing method were used to etch polysilicon for the purpose of studying influence of the water jet in the composite etching process, and a set of best parameters are summarized combined with laser parameters. Specifically works were done as follows:(1) The study of effect of water jet process parameters to etching results. Studying the effect of speed of water jet to etched grooves’ surface morphology and depth, the results indicate that the introduction of the jet can improve the combine etching quality effectively, and more obvious improvement is produced as higher water speed. Combined etching method improve the defects of crack, recast more obvious than direct laser etching. Studying the effect of speed of jet to the depth of groove, results indicate that jet’s function of impact and cooling play a different role since the jet’s speed changed which lead to the rule that grooves’ depth lead after an initial drop. In addition, the etching results at the case of static water was studied, finding that more defects of cracks and slag were produced, and the depth of groove is not as laser direct etching and depth produced by combined etching at high speed of jet. Studying the effect of jet’s speed and angle to the width of the grooves, found that the higher speed of the jet can increase the width of grooves, and the higher angle of jet formed narrower width of grooves.(2) Studying the effect of parameters of laser to the results of combined etching. The parameters include pulse width, repetition frequency were used to study their effects on combine etching grooves’ depth and cross-sectional shape, the results show that pulse width and frequency increasing at a certain range can increase the depth of the etching groove. However, due to the laser itself power limits, too high laser pulse width and repetition frequency, but will reduce the depth of groove. In addition, drop-shaped cross-sectional shape is easily produced when the pulse width is high, then the change of frequency has small effect on cross-section shape. The pulse width and repetition frequency were used to study their influence on flatness of groove of entrance contour that produced by combined etching. Analysis show that the higher pulse width can reduce flatness, and the change of frequency will lead to the emergence of roughness first high to low trend.(3) A set of perfect process scheme was summed by orthogonal test. Laser pulse width, frequency, input current, and speed of water jet were used as analytic factor, depth of groove, cross-sectional shape of the groove, and flatness of groove of inlet contour were used as standard. Studying the effect of factor to relevant standards by orthogonal test. Making a test to verify the best individual standard parameters that summed by orthogonal test. The final analysis got a technology program that the quality and efficiency of combine etching were all guaranteed.(4) Building the model of impact of water jet in combine etching method. Studying the effect of the angle and speed of the jet on the cross-sectional shape, then through relevant test to verify the simulation results. Using smoothed particle hydrodynamics(SPH) method to establish the model of impact of water jet, analyzed the jet’s impact function in combine etching process in detail, and on this account to study the influence on cross-sectional shape of grooves produced by angle and speed of jet. Finally, the rationality of established model was verified by test. The results showed that water with the higher speed will help to improve cross-sectional shape, and the jet with small incident angle is easy to form a V-shaped cross-section, and jet with a large incident angle is easy to form a standard U-shaped cross-section. In addition, the utilization of impact force produced by water jet with large incident angle is higher than the jet with small incident angle, and jet with small incident angle is better for slags’ removal that hang in slot, which make the width of groove more larger. The result of experiment showed that the established model is reasonable, to some extent, it could supplies convenience for the research of combine etching.